Human-operated (i.e., manned) utility vehicles, encompassing motorized pallet jacks, forklift trucks, buggies, and carts, are typically used in factories, warehouses, and distribution centers to move goods and people. “Automated vehicles”, as used herein, are commonly referred to in the industry by the term “automated guided vehicle” (AGV). The acronym AGV is a widely accepted term that encompasses a broad variety of industrial utility vehicles that transport goods and people without a driver. AGVs are used where automation can deliver key benefits of low labor cost, operation in hazardous environments, or special transport needs.
Modern advancements in flexible manufacturing have created a greater need for the use of AGV's. Flexible manufacturing systems integrate multiple automation steps to meet manufacturing demands, but also must link with material transport systems; therefore, an interface must exist between automated manufacturing cells and goods transport. Many AGV applications are technically feasible, but the initial cost and integration with existing systems is economically prohibitive.
Two general types of facilities have evolved since the 1950's: those employing manned utility vehicles for goods transport, and those using automated vehicles. In facilities where it is desired or necessary to operate both types of manned and automated vehicles, strict geographic separation has been necessary between the two types. This is done for worker safety as well as to prevent automated vehicle damage from potential collisions with manned vehicles. By separating work areas, designating certain areas off-limits to personnel, and rigidly defining automated vehicle travel paths, both modes of transport have been successfully utilized within a single facility.
A facility accommodating both manned and automated vehicles operating together in a shared space is believed desirable. This is rarely done for the reasons given above, but also because automated vehicles typically operate over fixed routes, while manned vehicles have free roaming ability. The basic problem has been, that at any given moment, an AGV does not “know” where manned vehicles are located, and the operators of manned vehicles have very limited knowledge of where AGV's are located; hence the long-standing separation.
The present invention solves this problem by a vehicle controller constantly monitoring the location and rotational orientation of both types of vehicles and sending control commands to the automated vehicles and control messages to the operators of manned vehicles. Further, the invention allows a new class of automated vehicle to be defined: one that navigates freely in the controlled space, directed by a machine control system that is aware of the instantaneous location of all vehicles. The operators of the free-roaming manned vehicles receive control messages warning them of the proximity of automated vehicles. The vehicle controller sends control signals to the automated vehicles causing them to stop, slow, or change direction if a collision with another vehicle is imminent. When the threat of a collision has abated the vehicle controller sends control signals to the automated vehicles causing them to resume travel on their selected paths.
It should be appreciated that tracking, guiding or navigating an automated vehicle in a three-dimensional space presents more stringent requirements than simply tracking a manned vehicle. The necessity of very accurately determining the position and the rotational orientation of the automated vehicle presents a significant difficulty. While sensing the position of an automated vehicle is important, sensing rotational orientation, i.e., directional heading, becomes even more important in automated vehicle guidance. To accurately control an automated vehicle, rotational resolution one or two orders of magnitude better than tracking systems is required. For example, while it may be sufficient to track a manned forklift truck within a coordinate space with a positional accuracy of one foot (thirty centimeters), and an orientation accuracy of ten degrees, an automated vehicle may require a position accuracy of a fraction of an inch (about five millimeters) and an orientation accuracy of a few tenths of a degree.
Rotational orientation sensing is also critical in materials handling applications, where goods may be stored in chosen orientations; for example, with carton labels aligned in a particular direction or pallet openings aligned to facilitate lift truck access from a known direction. A position determination and angular orientation determination method and apparatus that can be utilized as both a tracking system for manned vehicles, and as a guidance system for automated vehicles, using a single sensor on each vehicle, is therefore desired. Such an improved method and apparatus must reduce or remove the shortcomings of current methods, provide general applicability, and offer high accuracy.
The aforementioned parent U.S. application Ser. No. 11/292,463 describes a number of prior art technologies that have been applied to position determination' in one, two, and three dimensions. Some prior art technologies lack the ability to determine a vehicle's rotational orientation, which is critical for guidance. A few methods support a rotational orientation ability, but suffer other shortcomings in practical use. For example, laser guidance systems have the ability to determine rotational orientation, but are limited to scanning in a horizontal direction where obstructions can block the laser's field of view. Optical methods are known that view in the direction of walls where position markers also can be obscured. Other optical methods view toward the floor where position markers may be obscured by debris or be readily damaged.
The present invention of managing manned and automated utility vehicles in a coordinate space incorporates the methods the parent U.S. application Ser. No. 11/292,463 for position and rotational orientation determination of the vehicles. The present invention also utilizes the disclosure of U.S. application Ser. No. 12/319,825 filed Jan. 13, 2009, entitled “OPTICAL POSITION MARKER APPARATUS” and U.S. application Ser. No. 12/459,728 filed Jul. 7, 2009, entitled “METHOD AND APPARATUS FOR COLLISION AVOIDANCE”, which are hereby incorporated by reference.